1. Field of the Invention
The present invention relates generally to safety devices for fluid handling systems and, more specifically, a system which automatically shuts down an air heating furnace in the event of detection of unsafe levels of carbon monoxide in or around the heated air duct of the furnace or in the furnace flue pipe.
2. Description of Related Art
The spate of injuries and deaths caused by accidental leakage of carbon monoxide gas from malfunctioning furnaces has spawned the invention of a number of systems for automatically interrupting flow of fuel to the furnace upon a detection of unsafe levels of carbon monoxide. Heretofore, the prior art systems have relied on detection devices positioned in the "living space" i.e. the space occupied by humans. Examples of such prior art systems are shown in U.S. Pat. Nos. 4,088,986 (Boucher), 4,263,928 (Kobayashi et. al.), 4,787,410 (Fujieda et. al.), 4,974,624 (Gotanda), 5,419,358 (Sun), 5,722,448 (Dourado), and Japanese Patent Abstracts 57129974 and 57163786.
U.S. Pat. Nos. 5,638,847 (Hoch, Jr. et al.) and 5,671,773 (Park) disclose sensors for detecting the flow of liquids.
U.S. Pat. No. 5,651,248 (Kawamara) shows a sensor for detecting the accumulation of particulate matter.
U.S. Pat. No. 5,550,375 (Peters et al.) discloses a system for detecting gases by utilization of a spectrometer.
U.S. Pat. No. 5,730,170 shows a burner cutoff system responsive to accidental fire.
None of the above inventions and patents, taken either singly or in combination, is seen to disclose a system wherein fuel is shut off from a furnace burner upon detection of unsafe levels of carbon monoxide either interiorly or exteriorly of a furnace heated air duct or in the furnace flue pipe as will subsequently be described and claimed in the instant invention.